I've just searched the datasheet of the FT232R USB UART IC used in the Mini Breakout Board, and apparently this IC has an integrated level converter for interfacing 1.8V and 5V logic, so I'll say that a logic level converter is needed. You can check the complete datasheet here: FT232R Datasheet
For the USB port, the Edison Module Hardware Guide, page 15, says: "All Edison I/O (with the exception of USB) uses 1.8 V signaling.".
Let us know if this information was helpful. Have a nice day!
Thanks for the reply.
I took a look at the FTDI FT232R Data Sheet and yes, there is a logic level conveter to the RS232 application but that is to pull up the voltage from 5 V to the 9 V required by the RS232 interface.
In the MCU UART example there is no logic level converter. While it makes sense to convert the UART signals to the 1.8 V needed by the Edison, it would be very helpful for my Edison add-on board design activities to see the schematic for the Mini breakout board and understand how the signals to/from the Edison are being handled. I'd hate to connect the wrong voltage inadvertently and destroy one of my few precious Edisons while the supply of these is so scarce!